A hydraulic press for molding or forming an article is known, which press includes a frame having a top unit, a base unit, and rods tieing the top and bottom units together; a slide having the upper half of a mold secured thereto and vertically moveable by a first pair of hydraulic cylinder units into a first position; a fixed bed having the lower half of a mold secured thereto; a main hydraulic cylinder and piston ram for vertically moving the slide into a second position where the mold halves are engaged and the article formed by pressure from the ram; and hydraulic means for separating the mold sections for removal of the article and for return of all parts to their original positions.
To complete the process, however, one type of hydraulic press requires a long stroke of the main ram requiring additionally a high degree of compression of the large volume of fluid required, both the long stroke and high compression disadvantages.
Another example advantageously restricts the stroke of the main ram and reduces the compression required of the fluid for the shorter stroke; however, once the ram is in position for the main pressing movement against the slide, a plate or shim must be inserted by mechanical equipment between the ram and the slide with a thickness depending upon the desired travel of the slide. Thus, due to the necessity of interrupting the process for a mechanical insertion of a plate of a certain thickness from a large number of plates of different thicknesses, the process is not fully programmable, and requires an additional step and element to transmit force from the ram to the slide.
Yet another example involves an attempt to clamp the slide to outer cylinder posts for a shorter stroke with less compression; however, the clamping is not positive, resulting in unsatisfactory forming.